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There are two types of electrical currents: direct current (DC) and alternating current (AC). Direct current flows in a single direction along wires. Alternating current flows back and forth, rapidly switching direction many times per second.
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Direct Current (DC) & Alternating Current (AC) Electricity

There are two types of electrical currents that can flow through wires: direct current (DC) and alternating current (AC).

Direct current (DC) electricity flows in the same direction all the time through an electric circuit. The electrons that carry the electricity in a wire mostly move in one direction in a DC circuit. A flashlight with its batteries, bulb, and wires is a common example of a DC circuit.

The outlets in our homes provide alternating current (AC) electricity. The flow of electrons in an AC circuit switches direction very quickly - 60 times every second! The electrons first flow one way, then the other. However, the electrical devices we use don't care which direction the electrons are moving, since the same amount of current flows through a circuit regardless of the direction of the current.

Electric power distribution networks which deliver electricity to our homes are set up to handle alternating current electricity. Space weather storms can cause flows of direct current electricity in the electrical power grid. Since the grid was designed to used AC electricity but not DC electricity, the space weather induced direct currents can damage or destroy some types of equipment, such as voltage transformers.

Last modified February 17, 2009 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF